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Helium
Helium '''is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odourless, tasteless, non-toxic, inert monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions. Next to hydrogen, it is the second most abundant element in the universe, and accounts for 24% of the elemental mass of our galaxy. Characteristics Helium is used in cryogenics (its largest single use, accounting for about a quarter of production), the cooling of superconducting magnets, particularly the main commercial application in MRI scanners. Helium's other industrial uses as a pressurizing and purge gas, and a protective atmosphere for arc welding and processes (such as growing crystals to make silicon wafers), account for half of its use. In scientific research, the behaviour of two fluid phases of helium-4, helium I and helium II, is important to researchers studying quantum mechanics (in particular the phenomenon of superfluidity) and to those looking at the effects that temperatures near absolute zero have on matter (such as superconductivity). Being present in the universe in masses more than 12 times those of all the heavier elements combined. Helium's abundance is also similar to this in our own Sun and Jupiter. This high abundance is due to the very high binding energy (per nucleon) of helium-4 with respect to the next three elements after helium (lithium, beryllium, and boron). This helium-4 binding energy also accounts for its commonality as a product in both nuclear fusion and radioactive decay. Most helium in the universe is helium-4, and was formed during the Big Bang. Some new helium is being created presently as a result of the nuclear fusion of hydrogen, in all but the very heaviest stars, which fuse helium into heavier elements at the extreme ends of their lives. '''Helium III (He-3) is a light, non-radioactive isotope of helium with two protons and one neutron. It is sought for use in nuclear fusion research. The helion, the nucleus of a Helium III atom, consists of two protons but only one neutron, in contrast to two neutrons in ordinary helium. Its existence was first proposed in 1934 by the Australian nuclear physicist Mark Oliphant while based at Cambridge University's Cavendish Laboratory, in an experiment in which fast deuterons were reacted with other deuteron targets (the first demonstration of nuclear fusion). Helium III as an isotope, was postulated to be radioactive, until helions from it were accidentally identified as a trace "contaminant", in a sample of natural helium (which is mostly helium-4) from a gas well, by Luis W. Alvarez and Robert Cornog in a cyclotron experiment at the Lawrence Berkeley National Laboratory, in 1939. The presence of Helium III in underground gas deposits implied that it either did not decay, or had an extremely long half-life compatible with a primordial isotope. Helium III is proposed as a second-generation fusion fuel for fusion power uses. Tritium, with a 12-year half-life, decays into Helium III, which can be recovered. Irradiation of lithium in a nuclear reactor — either a fusion or fission reactor — can also produce lithium, and thus (after decay) Helium III. Value Helium: The base value of each unit of ranges between 1 and 8Ð per unit, with up to 10 units being found at any one time,. Presence on Mars: Very Common, Helium III: The base value of each unit of ranges between 1 and 10Ð per unit, with up to 8 units being found at any one time, Presence on Mars: Common, Category:Chemical elements